Regional integration is often considered a means to improve member countries’ attractiveness to foreign direct investment (FDI). But regional integration agreements (RIAs) as well as FDI are too diverse to allow for generalized verdicts. Our case studies on Mercosur in Latin America, ASEAN and SAARC in Asia, and SADC in sub-Saharan Africa caution against high expectations in several respects. First, country-specific factors were often more important as a stimulus to FDI than regional integration per se. Second, member countries are unlikely to equally share RIA-induced FDI inflows, even though the larger and richer members are not necessarily the winners taking all. Third, the regional heavyweights Brazil, China, India, and the Rep. of South Africa have played a minor role so far in fostering effective regional integration through outward FDI.